TORONTO - The pitch of one's voice appears to matter in the political trenches, at least according to new research that suggests voters are drawn to candidates with more sonorous tones.

The study conducted at McMaster University in Hamilton, and published Monday in the journal Evolution and Human Behavior, used recordings of nine U.S presidents going back to Harry Truman.

The team used computer software to manipulate the voices found in online archival recordings at Michigan State University, creating a higher-pitched version and a lower-pitched version of each.

"There's been a lot of work done on perceptions of politicians in other domains, you know, physical attractiveness and facial masculinity, and we just wanted to look at it in a domain that hadn't been studied yet, which was voice pitch," said lead author Cara Tigue, a doctoral candidate in the department of psychology.

The 125 subjects who participated in this portion of the study were asked to listen to both versions of the voice and express their preferences on a variety of dimensions, such as trustworthiness, leadership, intelligence, dominance, intelligence and attractiveness.

Overall, the participants favoured the lower-pitched voices.

The subjects were also asked whom they would prefer to vote for in peacetime, and in times of war.

Previous research has found that men's voices that have a lower pitch are perceived as more dominant, she said, and other studies have found that people can accurately assess physical strength from the voice.

"So we think that people are paying attention to these types of cues when they're choosing a lower-pitched voice."

In a second study of men's voices, which didn't involve U.S. presidents, 40 other participants also showed a preference to vote for the candidate with the lower-pitched voice.

The researchers conclude it is possible that artificially lowering one's voice pitch in audio recordings could help candidates gain votes.

Tigue said it's probably something that political strategists have been aware of for a long time.

"There's some anecdotal evidence that (former British prime minister) Margaret Thatcher ... went through voice training to actually speak in a lower-pitched voice," she said.

"I really just think that it just suggests that men with lower-pitched voices may have some sort of advantage. I don't know what political strategists will decide to do with that information."

She's planning other studies to look at female candidates, as well as Canadian politicians. She said U.S. presidents were used this time because the researchers were following precedent; several previous studies had looked at American leaders to determine perceptions — for instance, of facial masculinity.

As for voters, Tigue said the findings provide information about how certain perceptions could influence them.

"But we don't want to make any recommendations about what people should or shouldn't do when they're voting," she added.